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A versatile, modular in situ high-intensity monochromatic illumination set-up installed on a standard Q-band ESR spectrometer equipped with a cryostat and probe head for measurements at cryogenic temperatures, which can be easily assembled from commercially available optical components is presented. Using as monochromatic light sources pig-tailed laser diodes (LDs) or fiber-coupled light-emitting diodes (LEDs), a high efficiency of the light transfer (more than 95%) through an optical guide inserted in the sample holder is achieved in the sample area of the microwave cavity. With various LEDs and LDs, one can perform ESR in situ illumination experiments from UV to far-IR, in both cw and pulse mode. Its operation is illustrated with an experiment revealing the presence of certain ESR silent defects in oxygen-doped floating-zone ultrapure Si samples irradiated at room temperature with high-energy–high-fluence electron beams and pulse annealed up to 300 °C. New information is obtained by comparing the ESR spectra recorded at T = 120 K, without and with 1.06 µm across-the-gap in situ illumination.

The results of the present Q-band electron spin resonance (ESR) investigation on amber colored cubic boron nitride (cBN) crystalline superabrasive powder (BORAZON CBN400) offer further support to the hypothesis that impurity ions with high natural abundant zero nuclear spin isotopes, distributed non-uniformly, are involved in the structure of the observed paramagnetic centers. One could thus explain the absence of any hyperfine structure in the multifrequency electron spin resonance spectra of both presently and previously investigated cBN crystalline powders and single crystals. The scanning electron microscopy, cathodoluminescence and photoluminescence studies performed on single crystallites selected from the same cBN400 batch further confirm the presence of electro- and photo-luminescent active impurity related centers, non-uniformly distributed in the cBN crystallite host lattice. The observation of an intense and reproducible thermoluminescence spectrum, up to high radiation doses, attributed to several trapping centers involving impurities, is also reported here.

Previous electron spin resonance investigations correlated with data from cathodoluminscence and photoluminescence measurements have shown that impurity ions consisting mainly of isotopes with zero nuclear moments are involved in the structure of the observed paramagnetic point defects. In the present microstructural and compositional investigation we demonstrate that oxygen, carbon and silicon impurity atoms exhibiting low natural content of isotopes with non-zero nuclear spin are indeed present in cBN crystallites selected from amber coloured BORAZON CBN400 and CBN 500 super abrasive powders, as well as in the black coloured BORAZON CBN1000 and CBN Type 1. It is also shown that aggregates of impurity atoms are present next to the extended cBN lattice defects, which could explain the non-uniform distribution of the electro- and opto-active impurities reported in a spectroscopy investigation.

The production and thermal stability of the irradiation paramagnetic point defects (IPPDs) in the as-grown, standard float-zone silicon (STFZ) and oxygen doped float-zone silicon (DOFZ) irradiated at room temperature with high fluence 3.5 MeV (1 × 1017 cm−2) low energy and 27 MeV (2 × 1016 cm−2) high energy electrons were investigated by Electron Spin Resonance (ESR). The nature and concentration of the IPPDs identified in the as-irradiated and isochronally annealed up to 300 °C samples by ESR measurements under intense above the gap 1.06 µm in-situ laser illumination, were found to depend on oxygen concentration and electrons energy. While irradiation of STFZ with electrons produced as main IPPDs, besides divacancies, larger tetravacancy and pentavacancy cluster defects, irradiation of DOFZ resulted mainly in divacancies, vacancy-oxygen and interstitial oxygen-carbon impurity pairs. The observed variation in the nature of the main resulting IPPDs with the concentration of incorporated oxygen is explained by differences in the dominant defects production mechanisms. Thus in STFZ with lower oxygen concentration (1 × 1016 cm−3) the dominant production mechanisms are the direct defects formation from a chain of neighboring vacancies by a cascade of secondary recoils across the path of the high energy irradiating particle and the divacancies diffusion and trapping/aggregation. Meanwhile, in DOFZ with larger oxygen content (1.2 × 1017 cm−3) the primary vacancy and interstitial trapping by the oxygen and carbon impurities is the dominant defect production mechanism. Variations in the concentration and nature of the IPPDs observed during isochronal annealing are discussed in terms of defects thermal activated diffusion and recombination processes.

This paper describes the growth of CdF2 single crystals using the Bridgman method. Unwanted vapour reactions are avoided by using an argon atmosphere and glassy carbon crucibles. The installation for the growth of CdF2 single crystals is described in detail. Optical absorption of CdF2 crystals is shown for wavelengths of 200 to 800 nm. Transmission spectrum in the 2.5–10 μm range shows a low level of impurities which do not affect the optical qualities.

Paramagnetic Tl 2+ centers have been observed in SrCl 2 · TlCl crytals by X-irradiation in the 77–300 K temperature range. The resulting spin Hamiltonian parameters ( g = 2.0120 and A = 108.86 GHz) are close to the corresponding values earlier determined in alkali chloride hosts. The superhyperfine structure becomes partly resolved by warming-up above 130 K, a fact explained by the departure of the initial charge compensating nearest neighbour anion vacancy.

Uncoated plane parallel windows made from ultra-transparent KCl and NaCl crystals, which were grown by ‘injecting the reactive atmosphere’ (IRA) technique, have been tested as output windows in a high-power, high-repetition TEA CO2 laser, in various resonator configurations. Output power densities per pulse of 2 to 6 MW cm-2, which are 40% to 60% less than with 50% reflective coated ZnSe, have normally been obtained. The laser performances did not change after one year of operation and more than 107 pulses per window. No laser damage has been observed.

Additional multiplicity has been observed in the ESR spectra of CO2− and C03−3 molecule-ions trapped in single-crystal calcite. For both cases, this multiplicity is interpreted as superhyperfine structure arising from the isotopic substitution of naturally occurring 13C for 12C in neighboring carbonate ions. An analysis of the spectra based upon relative absorption line intensity ratios as well as considerations of symmetry suggest that the CO2− molecule-ion interacts primarily with but a single next-nearest-neighbor carbonate ion located in the plane of CO2−. For the case of CO33− molecule-ions, the spectral data suggest interaction with both the nearest-neighbor and next-nearest-neighbor carbonate ions. Details relating to the disposition of the interacting carbonate ions as well as the function of spin density transferred to these ligands are discussed.

The structure of the basal growth surfaces of cubic ZnS crystals grown from PbCl 2 flux was studied by both optical microscopy and multiple-beam interferometry. The surface microstructure was analyzed in connection with the growth rate and nature of added impurities.

Single crystals of ZnS have been grown by gradient transport in molten PbCl 2 . The morphology and structure has been studied by X-ray diffraction, optical microscopy under polarized light and etch-pit techniques.

NaCl single crystals, containing cationic impurities (Fe, Ni, Ca) exhibit after X-ray irradiation an ESR spectrum providing from some paramagnetic centers. The lines arising from different centers were identified and their spin Hamiltonian parameters were determined. Models are proposed from which the crystal field parameters have been calculated.

Crystals of KCl doped with bismuth exhibit after X-irradiation at room temperature the presence of a paramagnetic defect with tetragonal 〈100〉 symmetry. Based on the analysis of the ESR spectra a structural model based on a Bi 0 6 p 3 atom center is proposed. The strong axial crystal field is due to the presence of a vacancy in the first neighbourhood and/or a static Jahn-Teller distortion of E g character.

Single crystals of CaF 2 doped with uranium ions exhibiting a light red colour have been grown in an inert atmosphere. ESR spectra belonging to U 3+ centers unstable at room temperature could be observed only after UV-irradiation at liquid nitrogen temperature. The formation and annealing of these centers as well as the optical absorption date indicate that a new charge conversion mechanism is effective in such crystals.

A numerical analysis of the hyperfine components of all np 1 M 0 centers in alkali halides, for which ESR data are available, is performed in the frame of an earlier developed theoretical model. The resulting qualitative predictions concerning the off-center displacement of the M 0 atom in certain center-lattice host systems are compared with the available optical data.

There are several applications where solid devices are exposed to irradiation. Depending on the operational conditions (type of the particles, temperature, fluence) the physical properties of the exposed device degrades differently, reaching the point of electrical failure in very harsh enviroments. The radiation damage, starting already under low irradiation fluences, get more complex with increasing fluences due to the generation of various type of irradiation induced, electrically active, defects. Accord ingly, the defect characterization becomes a more difficult and costly task, requiring several complementary techniques to understand the detailed relation between the "microscopic" reasons as based on defect analysis and their "macroscopic" consequences for device performance. In this respect, we present the most powerful techniques employed and developed within the CERN RD50 Collaboration for investigating highly irradiated materials/structures : (i) Thermally Stimulated Current and Thermally Dielectric Relaxation Current techniques used for electrical characterization of bulk and interface defect states. With the obtained defect parameters several electrical characteristics of the devices could quantitatively explained; (ii) High Resolution Transmission Electron Microscopy and Electron Paramagnetic Resonance allowing the structural and chemical identification of the radiation induced defects.